a co-op student at a composite materials manufacturing company is attempting to determine how much of two different composite materials to make from the available quantities of carbon fiber and resin. the student knows that if 1 l of composite a requires 0.14 lb of carbon fiber and 1.1 lb of polymer resin while 1 l of composite b requires 3.1 lb of carbon fiber and 1.8 lb of polymer resin. if the available quantities of carbon fiber and resin are 16 lb and 11 lb, respectively, the amount of each composite to manufacture satisfies the system of equations: 0.14 xa 3.1 xb